Research Of Technologies In GPR Quantitative Detection Of Highway Roadbed And Surface

In our state, highway construction is developing fast, and there is a lot of testing work to do, but the traditional road detection method is beyond the modern need. To develop advanced detecting technology of roadbed and surface is of great importance. As a new road detecting method, ground penetrating radar has the continuous, rapid, undestructive advantages, and is being used extensively. However, it relys on the image qualitative more than quantitative analysis, which limits its applications.The report focus on two points of highway detection: physical index and defect. On one hand, we researched the dielectric properties of concrete, asphalt and soil with laboratory and field test, found out the relationship between dielectric constant and ratio, age of concrete, dielectric concrete and moisture content, compaction of soil. Dielectric model was established so that the thickness and moisture content could be measured quantitatively. On the other hand, we used forward modeling method todetermine typical GPR image of defects. There are totally 7 chapters in this paper. The first chapter introduces the current research situation, technology roadmap, innovation, et al. The second chapter presents the theory of GPR, common data processing method, the theory about dielectric properties. The third chapter reports the experimental results. We use GPR to detect many concrete board, asphalt concrete board, and soil samples, and then researched the dielectric properties of these three mixtures. As we found, the water in concrete is the main factor of concrete dielectric constant. Concrete maturation could be divided into two stages: the loss of free water and loss of bound water. We got the basic dielectric properties of asphalt concrete according to the measured data. The Topp and Alhatathi formulas were fixed, and it suits subgrade soil better. In the 4th chapter, we studied the dielectric models of these three mixtures according to the Lichtenecker equation. Results showed the concrete suits CRIM model, the asphalt concrete suits modified linear model, and the soil suits Looyenga model. The 5th chapter presents the feature of high defects in the GPR image. Most of the defects showed a common feature: diffraction cure. Both the sampling interval and antenna frequency could affect the resolution of GPR image. There is a high resolution with a little sampling interval and high antenna frequency. In the 6th chapter, we gave out some field highway detection examples, these examples confirmed the GPR quantitative detection of highway is possible. The last chapter presents the conclusions and next work requirments.Through the above research, we could learn the dielectric property of concrete and asphalt, establish the dielectric models of highway mixture materials, these key issues of highway GPR test could promote the GPR qualitative detection to quantitative detection.